1. Technical Field
The present invention relates to a semiconductor device having a sidewall and a method of manufacturing the semiconductor device.
2. Related Art
In recent years, semiconductor devices have been manufactured in which a logic circuit and a memory device such as Dynamic Random Access Memory (DRAM) are integrated onto one substrate. In such semiconductor devices, a transistor included in the logic circuit and a transistor included in a peripheral circuit of the DRAM are generally manufactured by the same process. For this reason, the transistor included in the logic circuit and the transistor included in the peripheral circuit of the DRAM have, in general, mutually the same structure.
On the other hand, it is often the case that the latest transistors have a sidewall and an extension region of a source and drain region. The sidewall covers a sidewall of a gate electrode. The extension region is located under the sidewall, that is, between the source and drain region and the channel region (for example, Japanese Unexamined patent publication NOS. 2000-269351, 2004-349372, 2008-78359, and 2006-196493).
In particular, Japanese Unexamined patent publication NOS. 2004-349372 and 2008-78359 disclose that an N-type MOS transistor and a P-type MOS transistor are made different from each other in width of the sidewall.
In the transistor included in the logic circuit, it is preferable that the on-state current is high. On the other hand, in the transistor connected to a capacitive element, such as the transistor included in the peripheral circuit of the DRAM, it is preferable that the leak current is small. Recently, miniaturization of semiconductor devices has progressed, and the gate length has been shortened with this progress. When the gate length is shortened, the on-state current of the transistor is increased and thus a leak current is easily generated. As mentioned above, in the semiconductor device in which the logic circuit and the transistor connected to the capacitive element are integrated onto one substrate, the transistor included in the logic circuit and the transistor connected to the capacitive element are generally manufactured by the same process. For this reason, in the transistor connected to the capacitive element, the leak current is caused to increase.